Experiments on local modification of lithium-borogermanate (LBG) glass with the composition (molar fraction, %) 25Li 2 O × 25B 2 O 3 × 50GeO by copper-vapor laser radiation on the main lasing lines (510.6 and 578.2 nm) in the visible range and on the sum frequency in the UV range (271 nm) are described. Local surface crystallization of LBG glass by a laser beam with 2 -15 mm crystals precipitated by means of laser heating of the sample at temperature somewhat below t g is demonstrated for the first time. X-ray phase analysis and confocal RS spectroscopy show that the polar phase LiBGeO 4 is the only phase formed as a result of crystallization. Crystallization obtains with UV-and visible-range radiation.Glasses in which a ferroelectric phase can be precipitated are of interest for creating active dielectrics, combining the advantages of glassy and crystalline materials, for different applications [1]. Among them researchers give special attention to glasses whose chemical composition is close to that of the crystalline phase precipitated in them, which makes it possible to preserve the composition of the glass practically unchanged in during the crystallization process and makes it possible in principle to convert all of the glass into a crystal. The degree to which the composition of the glass deviates from that of an analog crystal is determined by the possibility of obtaining bulk samples in the glassy state, because the crystallizability of the glass is maximized when the compositions are completely identical.Some of the best studied objects of this type are glasses in the lanthanum-borogermanate glass-forming system in the composition range close to the composition of the ferroelectric LaBGeO 5 , which possesses the structure of stillwellite [2 -4]. LaBGeO 5 crystals possess appreciable quadratic optical susceptibility and they admit partial substitution of the lanthanum ions by luminescing rare-earth ions with close ionic radius (Nd 3+ , Sm 3+ , Pr 3+ ) and the stillwellite structure being preserved, so that it can be used as an active medium for lasers with self-doubling of the frequency [5]. With the appropriate heat-treatment these crystals easily precipitate on the surface and in the interior of lanthanum-borogermanate glass, including in the form of microlayers and nanocrystals, making it possible to preserve the transparency of the material [2,6,7].In the last few years a number of interesting results have been obtained on the local crystallization of this glass by different types of laser beams [7 -11] in order to obtain on the surface or in the interior of the glass crystalline regions possessing nonlinearly optical properties and promising for the development of new types of elements for integrated optics.Thus far much less attention has been given to the investigation of lithium-borogermanate glasses, which near the composition (here and below, the molar ratio, %) 25Li 2 O × 25B 2 O 3 × 50GeO 2 are similar to the lanthanumborogermanate glasses in terms of crystallizability. In these glasses polar ...
